NOTE: Select a convenient normalization scale factor, N, which is approximately equivalent to the
net count for the reference specimen peak, and use this value of N for all analyses.
Normalizing to the reference specim en intensity compensates for long-term drift in X-ray tube
intensity. If intensity measurements are stable, the reference specimen m ay be run less
frequently and the net intensities should be normalized to the most recently-measured
reference intensity.
f. Determine the norm alized count, ÎAg, of an interference-free silver peak on the sample filter
following the same procedure. Use a short scan time for the silver peak (e.g., 5% of scan time for
analyte peaks) throughout the method.
g. Field blanks may be analyzed by scanning the 2-theta range used for the analyte and silver peaks
to verify that contamination of the filters has not occurred. The analyte peak should be absent. The
normalized intensity of the silver peak should match that of the media blank. Each laboratory
should determine the specifics of field blank use for its application. When contamination does
occur, the reason should be investigated and appropriate action taken. In practice, contamination
of field blanks is extremely rare and usually is not consistent across filters. The analysis of blanks
may be abbreviated if experience indicates that contamination is not likely with current field and
laboratory operations; however, occasional confirmation of non-contam ination is prudent.